1. Field of the Invention
The present invention relates to a disc-shaped knife rotary cutter equipped in a slitter-scorer or the like for cutting mainly soft plate-like bodies such as corrugated cardboard sheets or the like along a traveling direction of the sheets.
2. Description of the Prior Art
At first, description will be made of heretofore known disc-shaped knife rotary cutters for cutting soft plate-like bodies such as corrugated cardboard sheets or the like along a traveling direction of the sheets with reference to FIGS. 6 to 9, each of which depicts known cutters. FIG. 9 is a schematic front view showing a general construction of one of such rotary cutters in the prior art.
The known rotary cutter shown in FIG. 6 is of the type in which disc-shaped rotary knives 20a and 20b are mounted in an opposed and staggered relationship respectively on rotary shafts 11a and 11b disposed above and under a sheet pass line. The same disc-shaped rotary knives 20a and 20b are rotated at a somewhat faster circumferential velocity than a traveling velocity of a sheet (plate-like body) 1 forming a material to be cut, the sheet being fed and pinched between both knives to be sheared.
Next, the known rotary cutter shown in FIG. 7 is of the type that, like the above-described known rotary cutter, has a disc-shaped rotary knife 21 and a grooved backing roll 22 for supporting a traveling sheet 1 mounted on rotary shafts 11a and 11b disposed above and under a sheet pass line. Cutting is effected by a knife edge of a rotary knife 21 biting into a sheet (plate-like body) 1 forming a material to be cut, the knife projecting to the underside and being engaged with a groove R in the backing 22.
Further, the known rotary cutter shown in FIG. 8 is of the type that has, in place of the grooved backing roll 22 in the above-described known rotary cutter shown in FIG. 7, a brush-like backing roll 19 extending over the maximum sheet width. This backing roll 19 is mounted at the same position, and cutting is effected by a knife edge of a rotary knife 21 biting into a sheet (plate-like body) 1 forming a material to be cut, the knife projecting to the underside and being engaged with the brush portion. The disc-shaped rotary knives 21 in the known rotary cutters shown in FIGS. 7 and 8, also have their knife edge circumferential velocities set at somewhat faster than a sheet traveling velocity.
Now, a cutting position of a corrugated cardboard sheet or the like may be changed and set in various fashions depending upon a configuration of a box to be manufactured, and normally a disc-shaped rotary knife can be transferred from a storage position up to a cutting position by the intermediary of transfer/set means (carrier) and can be set (fixed) at the same position on the shaft via a movable key.
Now description will be made on a general construction of the rotary cutter portion with reference to FIG. 9. As illustrated in this figure, the construction is such that disc-shaped rotary knives 20a and 20b disposed in opposition to each other above and under a sheet pass line may be rotated synchronously in the opposite directions to each other by making gears 13a and 13b (fixedly secured to the shaft ends of rotary shafts 11a and 11b) mesh with each other, and a rotary drive torque may be obtained by making a gear 14 fixedly secured to a shaft end of a motor 12 mesh with the gear 13b. In this figure, reference numeral 23 designates bearings fitted in frames 24a and 24b for pivotably supporting the rotary shafts 11a and 11b. It is to be noted that in the rotary cutters shown in FIGS. 7 and 8, although there exists a little difference in conditions such as circumferential velocities of a grooved backing roll and a brush-like backing roll, it is ideal to perform forced driving, and from the point of overall construction, the FIGS. 7 and 8 cutters are similar to the rotary cutter shown in FIG. 9.
Next description will be made on the various disadvantages of the heretofore known apparatus. Since the generally known disc-shaped knife rotary cutters are constructed in the above-described manner, it is necessary to equip a pair of carriers 10a and 10b above and under a sheet 1 to act as a transfer/set means for upper and lower disc-shaped knives 20a and 20b (or a disc-shaped knife 21 and a grooved backing roll 22) that are opposed to each other at a cutting position on the sheet 1. However, in the known rotary cutter shown in FIG. 8, in view of the structure of the lower backing means (brush-like backing roll 19) the lower carrier 10b becomes unnecessary. In addition, in order to cause the above-described upper and lower knives or rollers to rotate in an opposed relationship, it is necessary to provide gears 13a and 13b, and so, there was a shortcoming in that the rotary shafts 11a and 11b and a driving apparatus for these shafts became complicated.
Furthermore, upon cutting a corrugated cardboard sheet, there is a problem in that when a knife edge of a rotary knife rotating at a high speed bites into a sheet 1, fine paper powder is produced. Moreover, not only would the produced paper powder adhere to the knife rotary shaft 11, but also a product sheet 15 would be conveyed to a downstream process step with the produced paper powder held adhered to its surface. With regard to removal of the paper powder, effective counter-measures have not been devised so far, and hence, at the time of printing in a box making machine (which forms a separate apparatus), the paper powder adhering to the product sheet surface would transfer to a printing plate and become a principal cause of printing blur.
By the way, the knives 20 and 21 employed in these cutters are commonly disc-shaped knives making use of metallic materials, and in order to realize good cutting capability, a circumferential velocity V.sub.o of the knife 2 is chosen faster than a traveling velocity V of the sheet 1. Thus, damage and deformation of the cutting surfaces are minimized and thus cutting capability is improved. In every one of the above-described type of cutters, cutting is effected by making a sharp knife edge of a disc-shaped knife 2 bite into the sheet (material to be cut) 1, and in view of the fact that the knife 2 is held in sliding contact with the material to be cut 1 at a super-high velocity, deterioration of cutting capability due to abrasion of the knife edge is inevitable, and so, degradation of appearance, linearity and dimensional precision of cut surfaces would arise.
Moreover, in a slitter-scorer that is used in the subsequent step of a double-facer for manufacturing a double-faced cardboard sheet, the paste 31 for sticking a single-faced corrugated cardboard sheet and a liner to each other does not reach a perfectly dried state when they are transferred to the slitter-scorer, and so, at the time of cutting, the following inconvenience would also occur. That is, there was a problem in that at the time of cutting the corrugated cardboard sheet 1, the above-described paste 31 (in an imperfectly dried condition) would adhere to the knife edge portion of the disc-shaped knife made to bite into the corrugated cardboard sheet 1 and would be solidified as shown in FIG. 9. Due to growth of the solidified paste 31, a dulled knife edge would be formed, resulting in damage and deformation of the cutting surfaces, and reduced cutting capability.
As described in the preceding paragraphs, a disc shaped knife rotary cutter in the prior art is constructed so as to cut a sheet traveling along a sheet pass line in the traveling direction by sheet cutting means, the cutting means consisting of a pair of disc-shaped knives disposed above and under the sheet pass line, a disc-shaped knife and a grooved backing roll having a groove formed on its outer circumferential surface so that the disc-shaped knife may fit in the groove with a predetermined gap space retained therebetween, or alternatively, a disc-shaped knife and a brush roll having brush elements planted on its outer circumferential surface. Therefore, the rotary cutter requires a rotary drive unit for rotating a pair of disc-shaped knives, a disc-shaped knife and a grooved backing roll, or a disc-shaped knife and a brush roll disposed in an opposed relationship above and under a sheet pass line in opposite directions to each other, and transfer/set means (carrier) for moving the disc-shaped knife or the grooved backing roll in the axial direction of their shafts in correspondence to a cutting position in the widthwise direction of the sheet. Accordingly, the rotary cutter had a disadvantage in that the entire apparatus became very large in size and complicated, and the manufacturing cost became high.
In addition, upon cutting and working a corrugated cardboard sheet, production of chip powder (paper powder) could not be avoided because of the cutter. The produced paper powder was sputtered to the periphery due to rotation of the disc-shaped knife and the like, and also the powder adhered to sheet support means and a drive section in the cutter or to the surfaces of the traveling sheet. Such condition caused degradation of printing quality in a box-making machine in the subsequent stage and/or remarkable deterioration of a working environment in a hygienic aspect.
Furthermore, in every one of the illustrated types of rotary cutters, during the period when a disc-shaped knife bites into a traveling plate-like body such as a corrugated cardboard sheet and penetrates therethrough, the disc-shaped knife and the plate-like body (material to be cut) would come into sliding contact with each other. Hence dulling of the sharpness of a knife edge of the disc-shaped knife caused by abrasion due to sliding friction cannot be avoided, and thus quality of the cutting surfaces is lowered, or a lot of time is necessitated for dismounting and mounting of a rotary knife for regrinding of a knife edge, which became a principal cause of greatly lowered productivity.
Moreover, in a disc-shaped knife rotary cutter used in a slitter-scorer, since a double-faced corrugated cardboard sheet is cut immediately after it was manufactured in a double-facer in the preceding process step, there was a problem in that paste adheres to a knife edge of a knife and solidifies and thereby a dulled knife edge is formed. There was a disadvantage that cutting capability was deteriorated (lowered) and also quality of the product was greatly degraded in appearance of the cut surfaces of the sheet.
The present invention has been proposed for the purpose of resolving the above-mentioned various problems involved in the prior art.